A projector is provided with an illuminating optical system, a color-separating optical system that separates light into first through third beams of colored light, first through third electro-optical devices that modulate the first through third beams of colored light to generate first through third beams of modulated light, a color combiner that combines the first through third beams of modulated light to create a composite light, and a projecting optical system that project the composite light. The projector further includes a λ/2 retardation plate provided on at least one of an incident side and an exit side of the third electro-optical device. Each of the λ/2 retardation plates has a first face open to the atmosphere and a second face in contact with a transmissive member.
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1. A projector for projecting and displaying a color image, comprising:
an illuminating optical system that emits illuminating light; a color-separating optical system that separates said illuminating light emitted from said illuminating optical system into first through third beams of colored light, each of which has one of three color components; first through third electro-optical devices that modulate said first through third beams of colored light separated by said color-separating optical system according to image information to form first through third beams of modulated light; a color combiner that combines said first through third beams of modulated light to create a composite light by reflecting said first and third beams of modulated light while transmitting said second beam of modulated light; a projecting optical system that projects the composite light emitted from said color combiner; and a λ/2 retardation plate provided on at least one of an incident side and an exit side of said first electro-optical device and another λ/2 retardation plate provided on at least one of an incident side and an exit side of said third electro-optical device, each of said λ/2 retardation plates having a first surface open to the atmosphere and a second surface in contact with a transmissive member.
6. A projector for projecting and displaying a color image, comprising:
an illuminating optical system that emits illuminating light; a color-separating optical system that separates said illuminating light emitted from said illuminating optical system into first through third beams of colored light, each of which has one of three color components; first through third electro-optical devices that modulate said first through third beams of colored light separated by said color-separating optical system according to image information to form first through third beams of modulated light; a color combiner that combines said first through third beams of modulated light to create a composite light by reflecting said first and third beams of modulated light while transmitting said second beam of modulated light; a projecting optical system that projects the composite light emitted from said color combiner; and a λ/2 retardation plate provided on at least one of an incident side and an exit side of said second electro-optical device, said λ/2 retardation plate having a first surface open to the atmosphere and a second surface in contact with a transmissive member, wherein said λ/2 retardation plate is affixed to one surface of said transmissive member, and said second electro-optical device includes a polarizing plate affixed to another surface of said transmissive member.
9. A projector for projecting and displaying a color image, comprising:
an illuminating optical system that emits illuminating light; a color-separating optical system that separates said illuminating light emitted from said illuminating optical system into first through third beams of colored light, each of which has one of three color components; first through third electro-optical devices that modulate said first through third beams of colored light separated by said color-separating optical system according to image information to form first through third beams of modulated light; a color combiner that combines said first through third beams of modulated light to create composite light by reflecting said first and third beams of modulated light while transmitting said second beam of modulated light; a projecting optical system that projects the composite light emitted from said color combiner; and a λ/2 retardation plate provided on at least one of an incident side and an exit side of said second electro-optical device, said λ/2 retardation plate having a first surface open to the atmosphere and a second surface in contact with a transmissive member, wherein said λ/2 retardation plate is affixed to one surface of said transmissive member, and said second electro-optical device includes a polarizing plate affixed to a second transmissive member other than said transmissive member to which said λ/2 retardation plate is affixed. 2. The projector according to
a direction of polarization of said first and third beams of modulated light incident on said color combiner is a first direction of polarization, while a direction of polarization of said second beam of modulated light is a second direction of polarization perpendicular to said first direction.
3. The projector according to
said illuminating optical system comprises: a polarized light generator for emitting said illuminating light as linearly polarized light having said first or second direction of polarization. 4. The projector according to
5. The projector according to
7. The projector according to
a direction of polarization of said first and third beams of modulated light incident on said color combiner is a first direction of polarization, while a direction of polarization of said second beam of modulated light is a second direction of polarization perpendicular to said first direction.
8. The projector according to
said illuminating optical system comprises: a polarized light generator for emitting said illuminating light as linearly polarized light having said first or second direction of polarization. 10. The projector according to
a direction of polarization of said first and third beams of modulated light incident on said color combiner is a first direction of polarization, while a direction of polarization of said second beam of modulated light is a second direction of polarization perpendicular to said first direction.
11. The projector according to
said illuminating optical system comprises: a polarized light generator for emitting said illuminating light as linearly polarized light having said first or second direction of polarization. |
1. Field of the Invention
This invention relates to a projector that projects and displays images.
2. Description of the Related Art
A projector usually comprises an illuminating optical system and liquid crystal panels for modulating light from the illuminating optical system responsive to image information (an image signal). The modulated light is then projected onto a screen by a projection lens.
The second liquid crystal light valve 900G comprises a liquid crystal panel 901G and polarizing plates 902Gi and 902Go at the incident and exit sides of the liquid crystal panel 901G, respectively. The polarization axes of the polarizing plates 902Gi and 902Go are set at right angles with each other. The incident side plate 902Gi transmits s-polarized light whereas the exit side plate 902Go transmits p-polarized light. With such a configuration, the s-polarized light incident on the second liquid crystal light valve 900G is converted to p-polarized light and then emitted.
The first liquid crystal light valve 900R comprises a liquid crystal panel 901R, a p-polarized light transmitting polarizing plate 902Ri, an s-polarized light transmitting polarizing plate 902Ro, and a λ/2 retardation plate 903R. The λ/2 retardation plate 903R is affixed to a glass plate 908, and the first polarizing plate 902Ri is affixed to the λ/2 retardation plate 903R. The s-polarized light incident on the glass plate 908 is converted to p-polarized light by the λ/2 retardation plate 903R, is transmitted through the p-polarized light transmitting polarizing plate 902Ri and is then converted to s-polarized light by the liquid crystal panel 901R and the s-polarized light transmitting polarizing plate 902Ro and emitted. The third liquid crystal light valve 900B has the same structure as the first light valve 900R.
The dichroic films of the cross-dichroic prism reflect s-polarized light more effectively than p-polarized light, and transmit p-polarized light more effectively than s-polarized light. Thus, the s-polarized light emitted from the first and third liquid crystal light valves 900R and 900B and the p-polarized light emitted from the second liquid crystal light valve 900G can be efficiently combined by the cross-dichroic prism 920.
In this Specification, the term "liquid crystal light valve" denotes a liquid crystal light valve in the broad sense, and it refers to a unit that comprises at least a liquid crystal panel and polarizing plates, and that may further comprises a λ/2 retardation plate. Note that a liquid crystal light valve in the narrow sense refers to a unit that includes a liquid crystal panel and polarizing plates and that does not include a λ/2 retardation plate.
The light illuminating the polarizing plate of the liquid crystal light valve generates heat to cause distortion of the polarizing plate occurs. Note that the amount of this distortion depends mainly on the intensity and distribution of the light which illuminates the polarizing plate.
In the aforementioned conventional projectors, the λ/2 retardation plates 903R and 903B contained in the first and third liquid crystal light valves 900R and 900B are sandwiched between the glass plate 908 and the polarizing plates 902Ri and 902Bi. For this reason, the distortion of the polarizing plate 902Ri causes distortion of the λ/2 retardation plate 903R.
In the case wherein the λ/2 retardation plate 903R is distorted in this manner, the distorted portions of the λ/2 retardation plate 903R (
An object of the present invention is thus to provide a technique for reducing chrominance nonuniformities in the images displayed by a projector.
At least part of the above and other objects of the present invention is attained by a projector for projecting and displaying a color image. The first projector comprises: an illuminating optical system that emits illuminating light; a color-separating optical system that separates the illuminating light emitted from the illuminating optical system into a first through third beam of colored light, each of which has one of three color components; first through third electro-optical devices that modulate the first through third beams of colored light separated by the color-separating optical system according to image information to form a first through third beam of modulated light; a color combiner that combines the first through third beams of modulated light by reflecting the first and third beams of modulated light while transmitting the second beam of modulated light; a projecting optical system that projects the composite light emitted from the color combiner; and a λ/2 retardation plate provided on at least one of an incident side and an exit side of both of the first and third electro-optical devices, the λ/2 retardation plate having a first surface open to the atmosphere and a second surface in contact with a transmissive member.
Since the λ/2 retardation plate is provided with one surface open to the atmosphere and its other surface in contact with a transmissive member, the distortion of the λ/2 retardation plate is reduced, and the chrominance nonuniformities in the images displayed are reduced accordingly.
In a preferred embodiment of the invention, a direction of polarization of the first and third beams of modulated light incident on the color combiner is a first direction of polarization, while a direction of polarization of the second beam of modulated light is a second direction of polarization perpendicular to the first direction.
In this arrangement, the color combiner can combine the first through third beams of modulated light effectively.
In a preferred embodiment of the invention, the illuminating optical system comprises: a polarized light generator for emitting the illuminating light as linearly polarized light having the first or second direction of polarization.
In this arrangement, the light incident on the first through third electro-optical devices has a uniform direction of polarization, and the light can be utilized effectively.
In a preferred embodiment of the invention, the λ/2 retardation plate is affixed to one surface of the transmissive member, and the electro-optical device includes a polarizing plate affixed to another surface of the transmissive member.
Although the λ/2 retardation plate and polarizing plate are provided on the same transmissive member in this arrangement, the distortion of the λ/2 retardation plate is reduced by the above stated mechanism and the chrominance nonuniformities are reduced in the images displayed.
In a preferred embodiment of the invention, the λ/2 retardation plate is affixed to one surface of the transmissive member, and the electro-optical device includes a polarizing plate affixed to a second transmissive member other than the transmissive member to which the λ/2 retardation plate is affixed.
In this arrangement also, the distortion of the λ/2 retardation plate is also reduced, and the chrominance nonuniformities are reduced in the images displayed.
Alternatively, the second projector comprises: an illuminating optical system that emits illuminating light; a color-separating optical system that separates the illuminating light emitted from the illuminating optical system into a first through third beam of colored light, each of which has one of three color components; first through third electro-optical devices that modulate the first through third beams of colored light separated by the color-separating optical system according to image information to form a first through third beam of modulated light; a color combiner that combines the first through third beams of modulated light by reflecting the first and third beams of modulated light while transmitting the second beam of modulated light; a projecting optical system that projects the composite light emitted from the color combiner; and a λ/2 retardation plate provided on at least one of an incident side and an exit side of the second electro-optical device, the λ/2 retardation plate having a first surface open to the atmosphere and a second surface in contact with a transmissive member.
This second projector has same function and advantage as the above first projector.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.
FIGS. 3(A), 3(B), and 3(C) are explanatory diagrams showing the polarized light generating optical system 160.
FIG. 6(A) is an explanatory diagram showing an alternate aspect of embodiment 3.
FIG. 7(A) is an explanatory diagram showing an alternate aspect of embodiment 4.
FIGS. 8 and 8(A) are explanatory diagrams showing the main part of embodiment 5.
FIGS. 9 and 9(A) are explanatory diagrams showing the main part of embodiment 6.
Here follows a description of the working of the present invention based on embodiments.
Light emitted from the illuminating optical system 100 is separated into colored light of the three colors red (R), green (G) and blue (B) in the color-separating optical system 200. The light of each color is modulated responsive to image information by the liquid crystal light valves 300R, 300G and 300B, respectively. The modulated light of each color is combined by the cross-dichroic prism 520 and projected by the projection lens 540 onto the screen SC to display a color image.
The light source 120 emits a beam of nearly parallel light. The light source 120 comprises a light emitting tube 122, a reflector 124 with a convex surface in the shape of an ellipsoid of rotation and a parallelizing lens 126. The light emitted from the light emitting tube 122 is reflected by the reflector 124 and the reflected light is converted by the parallelizing lens 126 into light that is nearly parallel to the light source optical axis 120ax. Note that a reflector which has a convex surface in the shape of a paraboloid of rotation may also be used as the light source.
The first lens array 140 has a plurality of small lenses 142 arranged in a matrix. The small lenses 142 are planoconcave lenses whose external shape, when seen from the z direction, is set so that it is similar to that of the illuminated area LA (liquid crystal light valve). The first lens array 140 divides the nearly parallel light beam emitted from the light source 120 into a plurality of partial light beams which are emitted.
The second lens array 150 has a plurality of small lenses 152 arranged in a matrix, like the first lens array 140. The second lens array 150 aligns the central axes of each of the partial light beams emitted from the first lens array 140 so that they are nearly parallel to the system optical axis 100ax, and forms the images of each of the small lenses 142 of the first lens array 140 upon the illuminated area LA.
As shown in the figure, the partial light beams emitted from the small lenses 142 of the first lens array 140 pass through the second lens array 150 to be focused within the polarized light generating optical system 160.
The polarized light generating optical system 160 correspond to the polarized light generator in the claimed invention. FIGS. 3(A) and 3(B) are explanatory diagrams showing the polarized light generating optical system 160. FIG. 3(A) is a perspective drawing showing the polarized light generating optical system 160, while FIG. 3(B) is a plan drawing showing a portion of it seen from the +y direction. The polarized light generating optical system 160 comprises a shading plate 62, a polarization beam splitter array 64 and a selective retardation plate 66.
As shown in FIG. 3(A), the polarization beam splitter array 64 contains a plurality of columnar transmissive members 64c, each having a section of parallelogram shape, which are adhered together. At the interface between each of the transmissive members 64c are formed polarized light separating films 64a and reflecting films 64b alternately. Note that multi-layer dielectric films are used as the polarized light separation films 64a while multi-layer dielectric films or metallic films are used as the reflecting films 64b.
The shading plate 62 comprises light-blocking surfaces 62b and open surfaces 62a disposed in alternating stripes. The shading plate 62 blocks the light beams entering the light-blocking surfaces 62b and transmits the light beams entering the open surfaces 62a. The light-blocking surfaces 62b and open surfaces 62a are arranged so that the partial light beams emitted from the first lens array 140 (
As indicated by the solid lines in FIG. 3(B), each of the partial light beams emitted from the first lens array 140 (
The selective retardation plate 66 comprises an open layer 66a and a λ/2 retardation layer 66b. Note that the open layer 66a is the portion upon which no λ/2 retardation layer 66b is formed. The open layer 66a functions to transmit incident linearly polarized light unaltered. On the other hand, the λ/2 retardation layer 66b functions as a polarization conversion element that converts linearly polarized light to another linearly polarized light having a direction of polarization perpendicular to its original direction. In this embodiment, as shown in FIG. 3(B), the p-polarized partial light beams that are transmitted through the polarized light separation films 64a enter the λ/2 retardation layer 66b. Therefore, the p-polarized partial light beams are converted to s-polarized partial light beams in the λ/2 retardation layer 66b and emitted. On the other hand, the s-polarized partial light beams reflected by the reflecting films 64b enter the open layer 66a so they are emitted unaltered as s-polarized partial light beams. To wit, non-polarized partial light beams that enter the polarized light generating optical system 160 are converted to s-polarized partial light beams and emitted. Note that by disposing a λ/2 retardation layer 66b on only the surfaces where the s-polarized partial light beams reflected by the reflecting films 64b are emitted, it is possible to convert the partial light beams that enter the polarized light generating optical system 160 into p-polarized partial light beams which are emitted (see FIG. 3(C)). As the selective retardation plate 66, it is possible to provide nothing in the open layer 66a portion and simply affix the λ/2 retardation layer 66b to the surfaces where the p-polarized partial light beams or s-polarized partial light beams are emitted.
As is evident from FIG. 3(B), the centers of the two s-polarized light beams emitted from the polarized light generating optical system 160 are displaced from the center of the incident non-polarized light (s-polarized light+p-polarized light) in the +x direction. The amount of this displacement is equal to one-half of the width Wp of the λ/2 retardation layer 66b (namely the size of the polarized light separation films 64a in the x direction). For this reason, as shown in
As described above, the plurality of partial light beams emitted from the first lens array 140 are separated by the polarized light generating optical system 160 into two partial light beams from each partial light beam, and also each is converted nearly completely into one type of linearly polarized light having a predetermined direction of polarization. The plurality of partial light beams with the predetermined direction of polarization are superimposed upon the illuminated area LA by means of the superimposition lens 170 shown in FIG. 2. The intensity distribution of the light illuminating the illuminated area LA becomes nearly uniform.
The illuminating optical system 100 (
The color-separating optical system 200 comprises two dichroic mirrors 202 and 204 and a full reflection mirror 208, separating the light beam emitted from the illuminating optical system 100 into colored light of the three colors red, green and blue. The first dichroic mirror 202 transmits the red component of the light emitted from the illuminating optical system 100 but reflects the blue and green components. The red light R transmitted by the first dichroic mirror 202 is reflected by the full reflection mirror 208 to head toward the cross-dichroic prism 520. The red light R emitted from the color-separating optical system 200 passes through a field lens 232 and reaches the red light liquid crystal light valve 300R. This field lens 232 converts the various partial light beams emitted from the illuminating optical system 100 into light beams that are parallel to its central axis. Note that the other field lenses 234 and 230 provided on the incident light sides of the other liquid crystal light valves 300G and 300B function similarly.
Among the blue light B and green light G reflected by the first dichroic mirror 202, the green light G is reflected by the second dichroic mirror 204 to head toward the cross-dichroic prism 520. The green light emitted from the color-separating optical system 200 passes through a field lens 234 and reaches the green light liquid crystal light valve 300G. On the other hand, the blue light B transmitted through the second dichroic mirror 204 enters the relay optical system 220.
The blue light B that enters the relay optical system 220 passes through an entrance-side lens 222, relay lens 226, full reflection mirrors 224 and 228 and an exit-side lens 230 (field lens) to reach the blue light liquid crystal light valve 300B. Note that the reason why the relay optical system 220 is used for the blue light B is so that the length of the optical path for the blue light B is longer than that of the other colors R and G, so by using a relay optical system 220, the blue light B entering the entrance-side lens 222 can be transmitted to the exit-side lens 230 unaltered.
The three liquid crystal light valves 300R, 300G and 300B modulate the three colors of light that enter them according to given image information (image signal), thereby generating modulated light beams. Each liquid crystal light valve comprises a liquid crystal panel and polarizing plates disposed on its incident side and the exit side. Note that details of the liquid crystal light valves are to be described later.
The cross-dichroic prism 520 combines the three colors of light (modulated light beams) modulated by the liquid crystal light valves 300R, 300G and 300B to generate composite light which represents a color image. The cross-dichroic prism 520 includes a red light-reflecting film 521 and a blue light-reflecting film 522 which are formed in an X shape on the interfaces among four rectangular prisms. The red light-reflecting film 521 is formed from a multi-layer dielectric film that reflects red light, while the blue light-reflecting film 522 is formed from a multi-layer dielectric film that reflects blue light. With the red light-reflecting film 521 and blue light-reflecting film 522, the three colors of light are combined to produce composite light that represents a color image.
The composite light generated by the cross-dichroic prism 520 is emitted in the direction of the projection lens 540. The projection lens 540 projects the composite light upon the screen SC to display a color image. Note that a telecentric lens can be used as the projection lens 540.
In embodiment 1, as described in
The s-polarized red light R separated by the first dichroic mirror 202 is reflected by the full reflection mirror 208 and enters the first liquid crystal light valve 300R. The liquid crystal light valve 300R comprises a liquid crystal panel 301R and two polarizing plates 302Ri and 302Ro provided on its incident side and exit side, respectively. In addition, a λ/2 retardation plate 303R is provided on the incident side of the liquid crystal panel 301R. The axes of polarization of the first and second polarizing plates 302Ri and 302Ro are set perpendicular to each other, so the first polarizing plate 302Ri is a p-polarized light transmitting polarizing plate which transmits p-polarized light and the second polarizing plate 302Ro is an s-polarized light transmitting polarizing plate which transmits s-polarized light. In this manner, the liquid crystal light valve 300R is provided with a λ/2 retardation plate 303R and two polarizing plates 302Ri and 302Ro like the liquid crystal light valve 900R shown in FIG. 10. However, where the λ/2 retardation plate 903R is sandwiched between the glass plate 908 and polarizing plate 902Ri in the conventional projector shown in
The s-polarized light incident on the first liquid crystal light valve 300R is converted to p-polarized light by the λ/2 retardation plate 303R. This p-polarized light is transmitted unaltered through the polarizing plate 302Ri and is modulated by the liquid crystal panel 301R and thereby, a portion of the light is converted to s-polarized light, and only the s-polarized light is emitted from the polarizing plate 302Ro.
The s-polarized green light G separated by the second dichroic mirror 204 enters the second liquid crystal light valve 300G. The second liquid crystal light valve 300G comprises a liquid crystal panel 301G, an s-polarized light transmitting polarizing plate 302Gi provided on the incident light side of the liquid crystal panel 301G and a p-polarized light transmitting polarizing plate 302Go provided on the light exit side. The s-polarized green light G entering the second liquid crystal light valve 300G is transmitted unaltered through the polarizing plate 302Gi and is modulated by the liquid crystal panel 301G and thereby, a portion of the light is converted to p-polarized light, and only the p-polarized light is emitted from the polarizing plate 302Go.
The s-polarized blue light B separated by the second dichroic mirror 204 is reflected by the full reflection mirrors 224 and 228 and enters the third liquid crystal light valve 300B. The third liquid crystal light valve 300B comprises a liquid crystal panel 301B, two polarizing plates 302Bi and 302Bo, a λ/2 retardation plate 303B, and a glass plate 308 to which the λ/2 retardation plate 303B and polarizing plate 302Bi are affixed. Note that the third liquid crystal light valve 300B is similar to the first liquid crystal light valve 300R, so we shall omit a detailed explanation thereof.
The reason why this embodiment is set up such that the first and third liquid crystal light valves 300R and 300B emit s-polarized light and the second liquid crystal light valve 300G emits p-polarized light is so that the light can be efficiently combined in the cross-dichroic prism 520. To wit, as described above, the cross-dichroic prism 520 includes a red light-reflecting film 521 and a blue light-reflecting film 522 which are formed in an X shape. These reflecting films 521 and 522 normally have excellent reflection characteristics with respect to s-polarized light. For this reason, the light to be reflected by these two reflecting films 521 and 522 is made to be s-polarized light and the light to be transmitted through the two reflecting films 521 and 522 is made to be p-polarized light. Thereby, nearly all of the s-polarized red light modulated by the first liquid crystal light valve 300R is reflected by the red light-reflecting film 521 and nearly all of the p-polarized red light modulated by the third liquid crystal light valve 300B is reflected by the blue light-reflecting film 522. In addition, nearly all of the p-polarized green light modulated by the second liquid crystal light valve 300G is transmitted by the red light-reflecting film 521 and blue light-reflecting film 522. Therefore, the cross-dichroic prism 520 can efficiently combine the various beams of polarized light emitted from the three liquid crystal light valves 300R, 300G and 300B. Note that in
As described above, in the projector of this embodiment, the λ/2 retardation plates 303R and 303B are provided with one surface open to the atmosphere and their other surface in contact with a transmissive glass plate 308 that does not change the direction of polarization. Accordingly, even if the polarizing plates 302Ri and 302Bi are distorted by heat, the λ/2 retardation plates 303R and 303B will not distorted so much. The λ/2 retardation plates 303R and 303B are able to convert the incident s-polarized light readily into p-polarized light, so the intensity of the p-polarized light emitted from the polarizing plates 302Ri and 302Bi on the incident light side and the intensity of the s-polarized light emitted from the polarizing plates 302Ro and 302Bo on the light exit side is not reduced compared to that of the conventional projector of FIG. 10. As a result, it is possible to reduce the chrominance nonuniformities in the color image displayed on the screen SC (
Note that as is clear from the above explanation, the first through third liquid crystal light valves 300R, 300G and 300B in this embodiment correspond to the first through third electro-optical devices of the claimed invention except for the λ/2 retardation plates 303R and 303B. In other words, the projector of this embodiment has the first through third electro-optical devices of the claimed invention, and additionally λ/2 retardation plates on the incident light sides. Note that the term "electro-optical device" is typically used in the narrow sense of an electro-optical device meaning the liquid crystal panel alone, but in this Specification, it refers to an electro-optical device in the broad sense of including the liquid crystal panel and polarizing plates. In addition, the s-polarized light emitted from the first and third liquid crystal light valves 300R and 300B correspond to the first and third beams of modulated light having a first direction of polarization in the claimed invention, and the p-polarized light emitted from the second liquid crystal light valve 300G corresponds to the second beam of modulated light having a second direction of polarization in the claimed invention.
In the first liquid crystal light valve 310R, s-polarized red light is transmitted through the polarizing plate 312Ri unaltered and enters liquid crystal panel 311R. The liquid crystal panel 311R converts a portion of the incident s-polarized light into p-polarized light and only the p-polarized light is emitted from the p-polarized light transmitting polarizing plate 312Ro disposed on the light exit side. The p-polarized light emitted from the polarizing plate 312Ro passes through the glass plate 318, enters the λ/2 retardation plate 313R, is converted to s-polarized light and emitted. The same goes for the third liquid crystal light valve 310B. In addition, the other constituent elements are identical to those of embodiment 1, so we shall omit a detailed explanation thereof.
In the projector of embodiment 2 also, the λ/2 retardation plates 313R and 313B are provided with one surface open to the atmosphere and their other surface in contact with a transmissive glass plate 318 that does not change the direction of polarization. Therefore, the distortion of the λ/2 retardation plates 313R and 313B due to that of the polarizing plates 312Ri and 312Bi can be reduced. As a result, the chrominance nonuniformities will be reduced in the displayed color image.
In contrast to the case of embodiment 1, in this embodiment it is possible to provide all s-polarized light transmitting polarizing plates 312Ri, 312Gi and 312Bi on the incident light sides of the three liquid crystal light valves 310R, 310G and 310B, and it is possible to provide all p-polarized light transmitting polarizing plates 312Ro, 312Go and 312Bo on the light exit sides. In this case, it is possible to design the orientation of the liquid crystals of the liquid crystal panels 311R, 311G and 311B identically. Therefore, in embodiment 2, the three liquid crystal light valves can be given a common design except for the λ/2 retardation plates so it is possible to reduce the number of types of parts.
Note that the projector in this embodiment correspond to the first and third electro-optical devices of the claimed invention with λ/2 retardation plates provided on the light exit side.
In embodiment 3 also, as shown in
In contrast to the case of embodiment 1, in this embodiment only one λ/2 retardation plate 323G is provided, so it has an advantage of being able to reduce the number of parts.
Note that the projector in this embodiment corresponds to the second electro-optical device of the claimed invention with a λ/2 retardation plate provided on the incident light side.
In embodiment 4 also, as shown in
In addition, in this embodiment, as with embodiment 2 (FIG. 5), it is possible to provide all p-polarized light transmitting polarizing plates 332Ri, 332Gi and 332Bi on the incident light sides of the three liquid crystal light valves 330R, 330G and 330B, and it is possible to provide s-polarized light transmitting polarizing plates 332Ro, 332Go and 332Bo on the light exit sides. The orientation of the liquid crystals of the liquid crystal panels 331R, 331G and 331B can be set identically. Therefore, in embodiment 4, the three liquid crystal light valves can be given a common design except for the λ/2 retardation plates so it is possible to reduce the number of types of parts. Moreover, in contrast to the case of embodiment 1, in this embodiment only one λ/2 retardation plate 333G is provided, so it has an advantage of being able to reduce the number of parts.
Note that the projector in this embodiment corresponds to the second electro-optical device of the claimed invention with a λ/2 retardation plate provided on the light exit side.
In embodiment 5 also, the two λ/2 retardation plates 303R and 303G are provided with one surface open to the atmosphere and their other surface in contact with the field lenses 232 and 230' that do not change the direction of polarization. Therefore, in the same manner as in embodiment 1, it is possible to reduce the chrominance nonuniformities in the displayed color image. Note that this is similarly applicable to the projector of embodiment 3 shown in
Note that the projector in this embodiment corresponds to the first and third electro-optical devices of the claimed invention with λ/2 retardation plates provided on the incident light side.
In embodiment 6 also, the two λ/2 retardation plates 313R and 313G are provided with one surface open to the atmosphere and their other surface in contact with the cross-dichroic prism 520 that does not change the direction of polarization. Therefore, in the same manner as in embodiment 2, it is possible to reduce the chrominance nonuniformities in the displayed color image. Note that this is similarly applicable to the projector of embodiment 4 shown in
Note that the projector in this embodiment corresponds to the first and third electro-optical devices of the claimed invention with λ/2 retardation plates provided on the light exit side.
As described above, in the projector according to the present invention, the λ/2 retardation plate is provided with one surface open to the atmosphere and its other surface in contact with a transmissive member that does not change the direction of polarization. By disposing the λ/2 retardation plate in this manner, the λ/2 retardation plate 303R will not distorted so much because of the distortion of the polarizing plate, so it is possible to reduce chrominance nonuniformities in the images displayed.
Note that this invention is in no way limited to the aforementioned working examples or embodiments, but rather various modifications are possible as long as they do not substantially deviate from it. For example, the following modifications are possible.
(1) In the aforementioned embodiments, the λ/2 retardation plate is provided together with a polarizing plate affixed to a glass plate, a cross-dichroic prism, field lens or other optical element, but the λ/2 retardation plate can also be provided independently. To wit, a λ/2 retardation plate simply affixed to a glass plate can be provided independently. In this case also, the λ/2 retardation plate is provided with one surface open to the atmosphere and its other surface in contact with a transmissive member that does not change the direction of polarization, so it is possible to reduce chrominance nonuniformities in the images displayed.
Note that a polarizing plate contained in a liquid crystal light valve may be affixed to a transmissive member to which a λ/2 retardation plate is affixed, as shown in
(2) In the aforementioned embodiments, the green beam of modulated light emitted from the second liquid crystal light valve is always made to be p-polarized light, and the red and blue beams of modulated light emitted from the first and third liquid crystal light valves are always made to be s-polarized light, but the colors of the light made to be p-polarized light or s-polarized light are not limited to these. For example, in
(3) In the aforementioned embodiments, an illuminating optical system 100 that emits s-polarized light or p-polarized light is used, but in the case wherein polarizing plates are provided on the incident light sides of the liquid crystal light valves, the incident light may also be non-polarized light. By doing so, it is possible to omit the polarized light generating optical systems 160 and 160' provided on the illuminating optical system. In this case, it is sufficient to provide the λ/2 retardation plates on the light exit sides of the liquid crystal light valves. However, by adopting the configuration as in the aforementioned embodiments, the light incident on the polarizing plates on the incident light side can be utilized effectively, so it has the advantage that a bright image can be displayed on the screen SC.
In addition, when an illuminating optical system 100 that emits s-polarized light or p-polarized light is used as in the aforementioned embodiments, the polarizing plates provided on the incident light sides of the liquid crystal light valves may be omitted. To wit, since the polarizing plates provided on the incident light sides of the liquid crystal light valves are used to increase the degree of polarization of the illuminating light, they may be omitted if the degree of polarization of the light incident on the liquid crystal light valves is sufficiently high. In this case, it is sufficient to provide the λ/2 retardation plates and polarizing plates on the light exit sides of the liquid crystal light valves.
(4) In the aforementioned embodiments, λ/2 retardation plates are provided on the incident light sides or light exit sides of the liquid crystal light valves, but it is also possible to combine two λ/4 retardation plates to achieve the function of a single λ/2 retardation plate. For example, in the projector of embodiment 1 (FIG. 4), there may be provided a first λ/4 retardation plate instead of the λ/2 retardation plate 303R for the first liquid crystal light valve 300R, and also provided a second λ/4 retardation plate on the light exit side of the field lens 232 (FIG. 1). In this case also, it is preferable for the λ/4 retardation plate to be provided with one surface open to the atmosphere and its other surface in contact with a transmissive member that does not change the direction of polarization.
(5) In the aforementioned embodiments, a cross-dichroic prism 520 is used as the color combiner of the present invention, but this is not a limitation. As the color combiner it is possible to use the two light-reflecting films 521 and 522 contained in the cross-dichroic prism 520 but formed upon glass plates, for example. Generally, as the color combiner it is sufficient to use something that reflects the incident first and third beams of modulated light but transmits the second beam of modulated light, thereby combining the first through third beams of modulated light.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
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